Bicycles are frequently equipped with an electric instrument intended to show to the operator measuring values like the actual speed of the bicycle or the actual distance covered by the bicycle. These electronic instruments can be mounted on a leg of the fork-shaped carrier unit in which the respective wheel is rotatably mounted. The operator can see the relevant measuring value on a display unit provided on the instrument. Some people like to have the instrument on the left-hand side of the forward wheel, others want to have it on the right-hand side of the wheel.